General Purpose Commands

The general purpose commands we will most likely use are: history, man, which and various redirects and pipes, to string together commands (to be discussed later): $\vert$, ;, %, $<$, $>$ and $>>$.

• which string gives location (path) of the executable file string if it exists; or if the executable is a UNIX command, it will tell you so.

  For example,

  % which lcurve
  /usr/local/ftools/bin/lcurve
  % which cd
  cd: shell built-in command.

• man command gives a synopsis of the command. The page is automatically formatted to accommodate the special format of the man page. man is short for manual, and the set of man pages comprise UNIX's online help manual and are usually consulted as a last resort, or for very in-depth information. The information these pages contain is usually encyclopedic, with some, but not many, examples. man pages frequently are more than a page long, with the reader accessing successive pages by hitting the space bar after reading the current page. The reader can quit the man page at any time by hitting q.

  Figure: Sample session showing use of cd and ls commands

  

• history lists the most recent commands you execute in the current shell.

  For example,

  % history
  1 22:24 man cd
  2 22:25 cd
  3 22:25 ls
  4 22:25 which ls
  5 22:26 history

  $\circ$ Exercise 3: Use which to see if netscape exists on our system. Also, see if emacs exists. What are these two programs' paths? Use man to find out more about the ls command. After you're done with this, how can you see which commands you've just typed?